1. Field of the Invention
The invention relates to multifunctional optical fiber bundles for image and signal transmission or sensor applications and particularly to a special kind of the bundles with reduced speckle noise (resulting from spatial inhomogeneity and asymmetry of radiation of specific fibers of the bundle) having ordered structure of fiber positions in its sensitive probe tip according to some prescribed rule.
2. Information Disclosure Statement
Multichannel optical fibers bundles provide very flexible tools for light transmission to and/or light receiving from some object. In general case such a bundles can be designed as a structure of fibers with prescribed positions of their ends in a sensitive probe tip bundled into specific light transmitting and light receiving channels.
Such bundles have many important applications. They can be used, for example, in various spectroscopic devices, process-photometers as a sensitive probe and light transmitting tool. Other applications of the bundles include high sensitive sensors of displacement or vibration measuring systems. Moreover, an ordered optical fiber bundle can be used as a light transmitting and reading device of raster type for linear detecting and light emitting components.
Many optical fiber bundles of various constructions have been designed and numerous methods of manufacturing of the bundles have been developed.
U.S. Pat. No. 3,244,894 describes photoelectric detection device utilizing randomized optical light conducting means which use a randomized single channel bundle.
U.S. Pat. No. 3,702,275 describes a fiber optic encoding-decoding apparatus and method for its fabrication. The apparatus employs an image encoding-decoding single channel bundle. The bundle is fabricated by steps of coiling the fiber into a thyroidal bundle of fiber convolutions. A randomization between fibers can be performed only for reproducing the image portion in random.
U.S. Pat. No. 3,383,192 describes a method of making fiberscope. It utilizes the fiber bundles that comprise a flexible structure of fibers.
U.S. Pat. No. 3,328,143 offers a method of making light-conducting optical multifiber structures which utilize a fiber optical image-transfer device.
U.S. Pat. No. 3,586,562 describes a method of making scrambled branched fiber optics. This method utilizes a mixed scrambling of branched fiber optic which is an initial layer of fibers on a drum of drawing machine. The fibers intermediate the tape strips are secured together by cement, and the fibers are then cut in the lacquered sections.
U.S. Pat. No. 3,674,452 claims a method of fabricating illuminated fiber optics. This method involves initially fabricating a fiber optic conduit, wherein a plurality of light-conducting fibers are formed in a bundle with a predetermined geometrical configuration at the first end and an identical geometrical configuration at the second end of the bundle.
U.S. Pat. No. 3,669,639 describes a method for production of a fused energy-conducting structure and also describes an apparatus for cementing a plurality of fibers in a simple parallel arrangement.
U.S. Pat. No. 3,586,563 offers a method for producing an optical fiber bundle by winding the fiber element onto a drum while it is rotated in one direction so that a layer of the helical wound windings is formed one channel structure on the drum.
U.S. Pat. No. 3,327,584 describes a fiber optic proximity probe, wherein transmitting and receiving fibers are bundled into channels with casual randomization ordering. The random numbers of transmitting or receiving fibers are placed snugly at the probe tip, wherein signals coming from the fibers near-by located fibers are mixed.
None of these inventions, however, discloses an optical fiber bundle whose fibers are arranged according to a programmable order in such a way that a plurality of fibers in the transmitting and receiving channels have spatial type of a layer or a matrix structure providing reduction of speckle noise and maximizing sensitivity as required for sensor and other applications. The speckle noise in each specific fiber is due to dynamic variation of spatially inhomogeneous speckle pattern resulting from the interference of many fiber modes. Collecting the radiation from many fibers included in the bundle can be used for averaging the speckle pattern and thus for reducing the speckle noise. Moreover, the modal noise in a multichannel optical fiber bundle, sensitivity of the signal on distance and angle between a reflecting surface, and the sensitive probe tip essentially depend on the specific structure in which the fiber ends of the optical bundle are ordered in its sensitive probe tip. For example, in optical fiber bundles with some specific ordering of the fiber in sensitive probe tip the sensitivity can be increased and the modal noise decreased in many times in comparison with nonordered bundle.